Many products, especially agricultural products such as raisins, dates and almonds, require cleaning. Cleaning often includes separating the heavier components from the lighter components. Since the desired product is commonly heavier than the material to be separated from the product, called debris, this separation is commonly done using airflow.
The simplest way of doing this is with a system called a blower. A relatively high volume blower is used to create an air flow through which the product to be cleaned is poured, like a waterfall. The cleaned product, being heavier, passes generally straight down through the air flow into a waiting container, onto a conveyer belt, etc. The lighter debris is carried away by the air flow and is typically collected in a debris collection hopper.
A second way of cleaning product uses an air leg. The product to be cleaned introduced into the lower portion of the vertically extending air leg, the air leg having a blower at its lower end. The blower provides a high volume air flow up through the air leg which passes through the product to be cleaned. The product is supported within the air leg on an angled screen so that the product continues down along the screen and exits the air leg while the lighter debris is separated out from the product and passes up through the air leg where the debris is collected, such as in a debris box.
A third conventional method uses a vacuum chamber in which a partial vacuum is created by a vacuum exhaust fan. The vacuum chamber is coupled to the upper end of a vacuum air leg. The lower end of the vacuum air leg overlies one end of a conveyor supporting the product to be cleaned. As the product to be cleaned passes under the lower end of the vacuum air leg, the lighter debris is pulled up into the vacuum air leg while the heavier product continues along the conveyor, falls off the end of the conveyor and is collected. When the separated light debris enters the vacuum chamber, the air speed drops suddenly so that the light debris then drops down and collects above an air lock which allows the debris to pass into a debris bin. The air lock, similar to a revolving door used at the entrances of stores and buildings, is used to minimize the seepage of air up in through the air lock while allowing the collected debris to pass out of the vacuum chamber. If an air lock were not used the vacuum exhaust fan would need to be much larger to get the same air flow through the vacuum air leg.